A drive circuit for an emitter switching configuration of transistors having a cascode connection of a power bipolar transistor and of a power MOS transistor control the saturation level of the configuration in applications which provide highly variable collector currents. The drive circuit includes a circuit operable to apply a varying voltage value to the control terminal of the bipolar transistor. A current/voltage converter senses a collector current flowing in the power bipolar transistor and controls conduction of a first transistor responsive thereto, the conduction of the first transistor controlling the conduction of a second transistor so as to vary the control terminal voltage in proportion to the sensed collector current of the power bipolar transistor.